Well, these aren't really panels. It's stucco/eifs with joints so the subs don't care if there are 3 sizes or 30 because the joints are located on site. It's not like a cement panel where a form needs to be made and they need to be modular. Regardless, I have no influence on this. The fact is there is very little constancy.
What you're describing seems to be the best method without a ruby. Once some simple modeling is done, a ruby is unnecessary true, however it's quite a lot of simple and repetitive modeling, which is what ruby's tend to excel at. If you had the option would you do it your way? Or would you bring in the CAD drawings, run Make Faces on it and then run a Make Bevels script on it and be done?
-Brodie